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Chemistry Forums for Students => Undergraduate General Chemistry Forum => Topic started by: HP on November 12, 2005, 12:33:34 PM

Title: Stech question
Post by: HP on November 12, 2005, 12:33:34 PM
Hi gyes,
I have this following stech question:
How much mmols of PO4 groups have in 1000mg of copolymer molecule having to monomer residues: ..-A-PO4-..B-SO3H-.. Monomer residues of A are 80% and these of B are 20%. The molecular mass of A is 161 and those of B is 203 resp. First i calculate the average mol mass of 1 monomer residue at the copolymer as follows:
(161)x0.8 + (203)x0.2 = 169.4
Then for calculating the mmols of PO4 groups at monomer A i used this formula for 1g polymer:
(1000/169)x 0.8 = 4.73mmol PO4groups in 1g polymer
My teacher said the right calculation is 1000/169 = 5.91mmol and he told me that at 169 consist the 80% of A and its wrong to increase this with 0.8
Tell me which calculation is right pls  ???